Step-by-step Loading Forming Technology And Simulation Of Large-scale Variable Wall Thick Head

With the development of nuclear energy,chemical industry,petroleum and other industries,head forgings as an indispensable and important component of major technical equipment,due to its large volume,complex structure,at high temperature,high pressure,Under harsh conditions such as long-term radiation,there is a higher requirement for product quality.For the large head,in order to make the outer shape and size and the comprehensive properties of the internal material structure meet the requirements of service,it is imperative to study the reasonable forming process of the head.However,at present,there is a significant gap between the existing large forging manufacturing technology in our country and abroad.Some high-end products and large forgings cannot meet the service standard,and gradually become a restriction on our country's heavy fitting.Prepare important factors for manufacturing and industrial development.In this paper,the SA508-3CL steel used for nuclear power head is taken as the research object,and the deformation temperature is 900 ?,the strain rate is 0.001 ml / s / 1,and the strain is 0.70.Using the Gleeble-1500 D thermal /mechanical simulator,the deformation temperature is 900 ?,the strain rate is0.001m2,the strain is 0.7,The thermal deformation behavior and dynamic recrystallization behavior of the material were studied.The thermal activation energy,Zener-Hollomon parameters,constitutive equation and dynamic recrystallization kinetic model of the material were obtained by linear regression analysis of experimental data.According to the established thermal deformation equation,taking the head of nuclear reactor pressure vessel as the research object,the forming process of step-by-step loading of nuclear power upper head is studied by means of finite element numerical simulation and scaling test.Under the condition that the load of the hydraulic press is satisfied,the forming mode,the optimization of the main technological parameters and the plastic deformation law of the head material are optimized.The main influencing parameters,the ratio of height to diameter of billet,the shape and size of punch,and the matching relationship between upper and lower die are analyzed in detail,and the influence of each technological parameter on the forming of head is summarized respectively.Finally,on the basis of satisfying the load of the existing hydraulic press,A reasonable step-by-step loading forming process scheme was determined.Based on the above-mentioned research,a set of test mould with the ratio of 1:8 was designed,and the step-by-step loading scale test of the head was carried out.The results show that the test size of the head is basically consistent with the designed size,and the load of the hydraulic press is satisfied.The rationality of the step-by-step loading forming process is proved,which provides a theoretical basis for the manufacture of the same type of head with variable wall thickness.